1. Field of the Invention
The invention relates generally to synthesis of molecular sieve complexes and more specifically to the use of certain bis(cyclopentadienyl) cobalt ion complexes as structure directing agents or templates.
2. Description of Related Art
The incorporation of metal complexes during the synthesis of molecular sieves is known to be useful for synthesis of zeolite "Ship-in-a-bottle" complexes. NaX zeolites have been synthesized around metal phthalocyanines (Balkus, et al, 1992; Balkus and Kowalak, 1992). In a few cases the metal complex may also function as a structure directing agent during crystallization. The metal complex bis(cyclopentadienyl)cobalt(III) ion, Cp.sub.2 Co.sup.+, has been reported to be a template for isostructural ZSM-51 and Nonasil in hydroxide and fluoride media as well as ZSM-45 (Balkus and Shepelev, 1993A, 1993B; U.S. Pat. No. 4,568,654). Nonasil is described in U.S. Pat. No. 4,556,549 as an all-silica clathrasil type molecular sieve. The metal complex is completely encapsulated as indicated by the x-ray structure that shows the largest openings to the nonasil cages are 6-membered rings (Behrens and van de Goor, 1994).
The formation of many molecular sieves depends on the presence of template molecules that affect the gel chemistry and/or act as a void filler (R. Szostak, 1989). Most of the templates that have been evaluated for molecular sieve synthesis are based on organic molecules, particularly aliphatic amines. By comparison, the structure directing properties of metal complexes are relatively unexplored. Cobalticinium ion, Cp.sub.2 CO.sup.+, has been shown to be a template for the clathrate type molecular sieves Nonasil and ZSM-51 as well as ZSM-45. In the case of ZSM-51, the template claimed for its synthesis was bis(cyclopentadienyl) cobalt(III) hexafluorophosphate. More recently, Cp.sub.2 CoOH was shown to be a template for the aluminum phosphate molecular sieves AlPO.sub.4 -5 and AlPO.sub.4 -16. Cp.sub.2 Co.sup.+ has been reported to produce the all-silica clathrasils octadecasil and dodecasil.
Recent work has thus indicated that the role of the metal and the effect of functionalizing the bis(cyclopentadienyl) rings may lead to new types of molecular sieves when these agents are used as structure directing agents. However, the structure directing effects for synthesis of molecular sieves are largely unpredictable and not well understood. The availability of novel molecular sieves would be beneficial in extending the range of zeolite type catalysts and in semiconductor applications.